Evaluating the Stability of Cellulose Nanofiber Pickering Emulsions Using MRI and Relaxometry

Area of Science:

• Colloid and surface science
• Materials science
• Biomaterials science

Background:

• Pickering emulsions offer an alternative to conventional emulsions.
• Cellulose nanofibers (CNFs) are emerging as effective stabilizers for Pickering emulsions.
• Understanding emulsion instability is crucial for their application and shelf-life.

Purpose of the Study:

• To investigate the instability mechanisms of oil-in-water Pickering emulsions stabilized by CNFs.
• To characterize the structural and dynamic changes within these emulsions over one month.
• To correlate MRI findings with emulsion composition and stability.

Main Methods:

• Utilized magnetic resonance imaging (MRI) relaxometry and diffusion methods.
• Investigated four Pickering emulsions with different oils (n-dodecane, olive oil) and CNF concentrations (0.5, 1.0 wt%).
• Employed fast low-angle shot (FLASH) and rapid acquisition with relaxation enhancement (RARE) sequences for imaging.

Main Results:

• MRI successfully visualized emulsion separation into free oil, emulsion, and serum layers.
• Voxelwise relaxation times (T1, T2) and apparent diffusion coefficients (ADCs) mapped emulsion components.
• Free oil and serum layer properties matched pure oil and water, while emulsion layer ADCs suggested restricted diffusion.

Conclusions:

• MRI relaxometry and diffusion are powerful tools for characterizing Pickering emulsion instability.
• Cellulose nanofiber concentration influences emulsion structure and molecular diffusion.
• The study provides insights into the long-term stability of CNF-stabilized emulsions.